ram: renesas: dbsc5: Improve dbsc5_send_dbcmd2() signature

ram: renesas: dbsc5: Improve dbsc5_send_dbcmd2() signature

Update dbsc5_send_dbcmd2() such that it takes multiple parameters
instead of one magic register content value. These parameters are
used to form the same resulting register value internally in the
dbsc5_send_dbcmd2() function, but from well defined input constants.
The new input constants are the operation code, channel, rank, and
operation argument. The argument is operation code specific, therefore
it is still a 16-bit magic number, but the rest of the arguments are
now split up. No functional change.

Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>